1. Technical Field
The present invention relates to a solid-state image sensor and an imaging device.
2. Related Art
Currently, the configuration of solid-state image sensors of a photoelectric conversion layer stacking type in which a photoelectric conversion layer including an organic material or the like that generates an electric charge in accordance with incident light is disposed on the upper side of a semiconductor substrate is proposed. According to this configuration, by disposing the photoelectric conversion layer having high photoelectric conversion efficiency in the upper portion of a read-out circuit such as a CMOS, a decrease in the thickness, a high aperture ratio, and high sensitivity of the imaging device may be achieved, which implements superior characteristics. These solid-state image sensors have appropriate characteristics for a miniaturized camera such as a camera phone module, which implements superior characteristics.
A CMOS image sensor that uses a photoelectric conversion layer has a characteristic in which the amount of signal electric charge generated through photoelectric conversion changed by using a voltage (an opposing voltage or a bias voltage) applied to the photoelectric conversion layer (for example, see JP-A-2006-094263 and JP-A-2005-353626). Generally, the voltage applied to the photoelectric conversion layer needs to be high, and accordingly, a high voltage generated using a voltage boosting circuit such as a charge pump method or the like that may be easily integrated with a sensor as an IC for relatively easy miniaturization is applied to the photoelectric conversion layer.
In imaging devices having the above-described configuration, in order to generate the signal electric charge using the photoelectric conversion layer, a configuration in which an upper electrode is disposed in the upper portion of the photoelectric conversion layer, a lower electrode is disposed in the lower portion of the photoelectric conversion layer, a voltage supplying means is connected to the upper electrode, and a voltage may be applied to the photoelectric conversion layer pinched between the upper electrode and the lower electrode is used. At this time, there is a case where only one location as a portion connecting the voltage supplying means and the upper electrode is disposed or a case where there is a plurality of connection portions and the distances from each connection portion to a sensor region are different from one another. In such a case, there is a possibility that the voltages applied to the photoelectric conversion layers of pixels configuring the sensor region are not uniform, and unevenness in the image occurs due to different amounts of a signal electric charge generated in the pixels, whereby the image quality deteriorates.
As a solution of the above-described problems, the wiring, the circuit, the via plug, and the like used for applying voltages are considered to be disposed such that a voltage is uniformly applied to the photoelectric conversion layers of the pixels. However, in consideration of the viewpoint of miniaturization of the pixels, it is especially difficult to form the circuits or the wirings so as to correspond to the pixels.
In JP-A-2005-353626, a configuration in which there is a plurality of photoelectric conversion layers stacked on a substrate, and a wiring, which has a flat shape, for connection with the upper electrode layer is disposed in the circumference portion of the upper electrode for applying a uniform voltage to the photoelectric conversion layers is disclosed. However, by configuring electrodes for supplying voltages in the circumference of the pixel region, the upper side of a semiconductor substrate may not be uniformly coated with a panchromatic (visible wavelength band general type) photoelectric conversion layer or the like, and the manufacturing process becomes complex, which leads to a decrease in the yield ratio and an increase in costs.
As described above, in solid-state image sensors in which a photoelectric conversion layer is stacked on a substrate, there is a room for further enhancement for how to supply the voltages to the upper electrodes used for applying voltages to the photoelectric conversion layer.
The present invention is to provide a solid-state image sensor and an imaging device capable of applying a uniform voltage to the photoelectric conversion layers disposed on the substrate.